The present invention is related to a control device for refrigerating equipment which is capable of automatically regulating the optimal operating conditions of the equipment.
To maintain the temperature of a refrigerated space and its low-temperature compartments within present limits, suitable thermostatic control devices are normally employed. These are primarily temperature sensors placed in contact with the evaporator or inside the refrigerated space and/or in the low-temperature compartments, and the regulator units associated with the sensors which are connected to the electrical circuitry of the refrigerating equipment's motor-driven compressor so as to be able to start and stop the motor-driven compressor depending upon the temperature reading of the sensors.
To eliminate the frost which accumulates during the operation of the evaporator following the condensation of the moisture present in the refrigerated space, the refrigerating equipment undergoes periodic defrosting cycles. These cycles are induced by stopping the compressor for periods of time which are sufficient to elevate the temperature in the evaporator, or through the use of a suitable heating element placed in contact with the external surface of the evaporator and connected to its electrical circuitry.
For this purpose, the thermostatic control device can be implemented so that the motor-driven compressor is stopped when the defrosting begins and the above-mentioned heating element is activated if so desired, and the operation is then reversed upon completion of the defrosting.
The thermostatic control devices currently in use are of the electrical or electro-mechanical type and are able to time, perhaps in combination with a more common timing device, semi-automatic or automatic defrosting cycles in the refrigerating equipment.
With a semi-automatic control device, the temperature of the refrigerated space can be varied within a manually predetermined range by manually presetting the control device in different regulative positions.
The defrosting cycle is then initiated by means of the manual operation of a specific momentary electrical switch which is associated with the control device and which is connected into the compressor's electric circuit, and is terminated automatically once the evaporator-determined temperature has been reached. In this circumstance, each defrosting cycle occurs after a relatively long period of time with respect to the previous defrosting cycle and can be initiated intermittently when the user so desires.
Moreover, during this cycle, the compressor is interlocked with the thermostatic control device and thereby maintains the refrigerated space at the selected temperature.
As a result, the air in the refrigerated space is constantly dehumidified, since the moisture is condensed on the surface of the evaporator which is constantly at below freezing temperatures even when the compressor is at rest. Therefore, this air has a notably reduced level of humidity, thus allowing the food to reach a higher level of dehydration.
With an automatic control device, regulation of the temperature in the refrigerated space is carried out in the above-described manner, while the defrosting cycle occurs differently.
In fact, every control device of this type is implemented in such a way as to automatically initiate the defrosting cycle after every start and stop operation of the compressor and to terminate the cycle upon reaching a predetermined temperature.
Thus, in comparison with the semi-automatic device, several defrosting cycles are carried out during the same amount of time. Consequently, the air in the refrigerated space is dehumidified less because the surface temperature of the evaporator is greater than 0 degrees C during each of the compressor's shut-off periods, thus causing the moisture which had condensed on the evaporator to return in part to the surrounding air.
This air then reaches a high level of humidity, thus lowering the level of dehydration in the food. However, the control devices in question, though allowing sufficient regulation of the temperature in the refrigerated space, don't allow the satisfactory indirect regulation of humidity in the same space to within determined limits as would be desired to assure optimal food-storage conditions in the refrigerated space.